This application to join the Consortium on Targeting And Regeneration as part of the Human Islet Research Network (HIRN) seeks to develop cell-based strategies to target pancreatic islets and overcome two central problems in type 1 diabetes: to (1) provide immunoregulation that is targeted to islets and shuts down autoimmune destruction without broad immune-suppression, and (2) deliver factors that improve ?-cell survival, regeneration and function. Advances in genetic modification of T lymphocytes have revolutionized therapeutic targeting in fields like oncology. T cells can be engineered to express chimeric antigen receptors (CAR) that direct CAR T-cells to specific antigens expressed by neoplastic cells whereupon they activate and cause tumor regression and elimination. These successes have prompted exploration of CAR technology with Tregulatory (Treg) cells the non-neoplastic disease settings, including type 1 diabetes. While those studies demonstrated safety, Treg cells ? which have the ability both to immunomodulate and deliver trophic factors supporting islet cell function, growth, regeneration and survival ? did not localize to sites where they may be needed (like islets or pancreas). This proposal is based on recent discoveries by our team that mouse Treg cells can be modified to express CAR's which bind modified antibodies to direct Treg localization to islets, and promote allograft tolerance in vivo. In addition our team members have generated and validated unique, high- quality monoclonal antibodies for purifying, investigating and targeting human islet cells. We hypothesize that human Treg cells can be modified to express chimeric antigen receptors that similarly target human islet cells. We postulate that developing these modular, cell-based targeting methods will produce novel clinical strategies to prevent T1D in high risk patients, to suppress autoimmunity and preserve ?-cell mass in patients with recent-onset T1D, and to deliver therapeutics to the pancreas for ?-cell expansion or regeneration in established T1D. In response to this RFA, we have formed a broad- based, complementary and interdisciplinary scientific team with expertise in human pancreatic islet biology, molecular targeting, immunotherapeutics, transplantation biology, and clinical trials. We propose three aims: 1) Develop antibody- directed CAR Treg cell targeting to human islets in vivo. 2) Develop strategies to enhance human islet targeting with split-receptor CAR Treg cells 3) Evaluate CAR Treg targeting to native pancreatic islets in mouse T1D models In addition, our team will bring to CTAR and HIRN substantial experience and new tools that could benefit the HIRN mission and its members.